Subscriptions are managed by the store where the purchase was made.
For Apple purchases, open device Settings, select your Apple Account, open Subscriptions, select Scanner App, and follow the cancellation steps.
For Google Play purchases, open Google Play, select your profile, open Payments & subscriptions, select Subscriptions, choose Scanner App, and follow the cancellation steps.
Cancelling prevents future renewal. It does not normally create an automatic refund for a previous charge.